1. Field of the Invention
The present invention relates to a plasma display panel, and, more particularly, to a power module for energy recovery and sustain of a plasma display panel.
2. Description of the Related Art
In a plasma display panel, alternating AC pulses are alternately applied to opposite ends of the panel in accordance with repeated charge and discharge operations until a discharge initiation voltage reaches a critical voltage. The plasma display panel starts generating visible light by gas discharge, when the discharge initiation voltage reaches the critical voltage. The AC pulse voltage is called a “sustain voltage”. The sustain voltage is generated by a sustain circuit. However, where such a sustain circuit does not perform an energy recovering function, a certain amount of energy is consumed in every interval of a sustain period. This energy consumption increases in proportion to a switching frequency. For this reason, an energy recovering circuit is used in addition to a sustain circuit, in order to minimize the consumption of energy generated in switching operations, and thus, to achieve an enhancement in efficiency.
FIG. 1 is a circuit diagram illustrating circuits for energy recovery and sustain of a general plasma display panel. A plasma display panel 100 may be represented by a plurality of equivalent capacitors respectively corresponding to a plurality of pixels. A scan circuit 110 is connected to the plasma display panel 100, in order to select the equivalent capacitors corresponding to a selected one of the pixels. A charge/discharge waveform adjusting circuit 120, a sustain circuit 130, and an energy recovery circuit 140 are sequentially connected to the scan circuit 110 at one side of the plasma display panel 100. Another sustain circuit 150 and another energy recovery circuit 160 are connected to the other side of the plasma display panel 100. The configuration and operation of the sustain circuit 150 and energy recovery circuit 160 are identical to those of the sustain circuit 130 and energy recovery circuit 140 on the left side of the plasma display panel 100.
The scan circuit 110 can select the equivalent capacitor which corresponds to a selected pixel of the plasma display panel 100. The charge/discharge waveform adjusting circuit 120 can adjust a charge/discharge waveform for charging/discharging the selected equivalent capacitor to a desired waveform. The sustain circuits 130 and 150 can apply a certain voltage to the plasma display panel 100 in order to maintain the plasma display panel 100 in a discharge state. The energy recovery circuits 140 and 160 can perform a switching operation using bidirectional switching elements Q1 and Q2 and an energy recovery capacitor 141 connected to the bidirectional switching elements Q1 and Q2, in order to charge or discharge the plasma display panel 100.
Typical energy recovery circuits 140 and 160 and sustain circuits 130 and 150 are integrated in a single power module, or are built in separate power modules. Where these circuits are integrated in one power module, two half-bridge type high voltage integrated circuits (HVICs) are also included in the power module. One HVIC controls switching elements of the sustain circuits 130 and 150, the other HVIC controls switching elements of the energy recovery circuits 140 and 160. In these architectures additionally a bootstrap capacitor is integrated in the power module. The bootstrap capacitor is connected to one of the switching elements of the energy recovery circuits 140 and 160. A drawback of this design is that it is not easy to control the switching operation of the switching element using the bootstrap capacitor.
In architectures, where the above-mentioned circuits are integrated in separate power modules, the bootstrap capacitor is not integrated in the power module of the energy recovery circuits, but is formed in a separate power module. However, a drawback of designs with separate power modules is the larger chip area.